WEDNESDAY, Oct. 17 (HealthDay News) -- Criminal investigators from the U.S. Food and Drug Administration on Tuesday visited the specialty pharmacy in Massachusetts linked to the meningitis outbreak that has killed 15 people and sickened 233, according to published reports.

An FDA spokesman said agents from the agency's Office of Criminal Investigations were at the Framingham-based drug company, but he provided no details. The office probes suspected violations of federal laws that are designed to protect public health, The New York Times reported.

A steroid manufactured by the company, the New England Compounding Center, has been linked to the meningitis outbreak. Last month the company voluntarily recalled three lots of the steroid, which is injected into patients for back and joint pain. The company has since shut down operations and stopped distributing its products, health officials said.

Two Democratic members of Congress -- Rep. Edward Markey of Massachusetts and Rep. Richard Blumenthal of Connecticut -- have asked the U.S. Justice Department to investigate whether the New England Compounding Center violated any federal laws or regulations, the Associated Press reported.

On Monday, the FDA issued warnings about additional drugs produced by the specialty pharmacy.

The FDA said it was investigating a report of a meningitis infection in a patient who got a different steroid than the type linked to the more than 233 infections nationwide.

The agency also said it was checking reports of fungal infection in a heart transplant patient given a cardiac solution made by the New England Compounding Center. The solution is used to paralyze heart muscle to prevent injury to the heart. But it's possible the infection could have come from a source other than the solution, the agency said.

The FDA said it was advising all health-care professionals to follow up with any patients who were given any injectable drug from or produced by the New England Compounding Center. These drugs include medications used in eye surgery, and the heart solution purchased from or produced by the company after May 21.

The New England Compounding Center is what's known as a compounding pharmacy. These pharmacies combine, mix or alter ingredients to create specific drugs to meet the specific needs of individual patients, according to the FDA. Such customized drugs are frequently required to fill special needs, such as a smaller dose, or the removal of an ingredient that might trigger an allergy in a patient.

On Tuesday, federal health officials said 19 more cases of fungal meningitis linked to the initial round of contaminated steroid injections have been reported, bringing the total number of cases to 231.

The number of deaths held steady at 15, the U.S. Centers for Disease Control and Prevention said.

There also have been two cases of what the CDC calls "peripheral joint infection," meaning an infection in a knee, hip, shoulder or elbow. These peripheral joint infections -- caused by injections of pain-killing steroids -- aren't considered as dangerous as injections near the spine for back pain that have been tied to the potentially fatal meningitis infections.

All of the 231 patients were thought to be injected with methylprednisolone acetate, a steroid often used for back and joint pain that investigators suspect was tainted with a common fungus, according to the CDC.

It's believed that as many as 14,000 people may have gotten injections of the steroid. The 14,000 figure includes not only people who got injections for back pain and are most at risk for meningitis, but also others who received injections for pain in their knees and shoulders.

Meningitis is inflammation of the lining surrounding the brain and spinal cord.

All of the infected patients are thought to have received the medication from the Massachusetts pharmacy, according to the CDC.

Health officials said they expect to see more cases of the rare type of meningitis, which is not contagious, because symptoms can take a month or more to appear.

Infected patients have developed a range of symptoms approximately one to four weeks following their injection. People who have had a steroid injection since July, and have any of the following symptoms, should talk to their doctor as soon as possible: worsening headache, fever, sensitivity to light, stiff neck, new weakness or numbness in any part of your body, slurred speech, the CDC said.

Infected patients must receive intravenous drugs in a hospital.

Compounding pharmacies like the New England Compounding Center historically started out as community-based neighborhood druggists. But over time, the practices of some compounding pharmacies have expanded, sometimes beyond their intended limits, experts explained.

According to the AP, this is not the first time the New England Compounding Center has encountered problems with contaminated injections. In 2007, the company settled a lawsuit that claimed that an 83-year-old man died in 2004 after contracting fatal bacterial meningitis from a shot produced by the compounding center. The pharmacy reached a settlement with the man's widow before the case went to trial, the AP said.

Compounding pharmacies aren't subject to the same FDA oversight as regular drug manufacturers are, and some members of Congress now say the meningitis outbreak highlights the need for more regulatory control.